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1374 SECTION 16: Environmental Injuries PATHOPHYSIOLOGY After submersion, the degree of hypoxic insult to the CNS determines the ultimate outcome. It was previously thought that parasympathetic activation of the diving reflex (i.e., bradycardia, apnea, peripheral vasoconstriction, and central shunting of blood flow) provided transient protection during submersion. However, in most cases, the diving reflex is overwhelmed by the stimulation of the sympathetic nervous system, yielding no meaningful protection. 5 Cerebral protection in cold water submersions most likely results from rapid CNS cooling before significant hypoxic damage occurs. Physiologic scoring systems 6,7 to predict drowning outcome have been devised but are not clinically helpful. The vast majority of patients who arrive at the hospital with stable cardiovascular signs and awake, alert neurologic function survive with minimal disability, whereas those who arrive with unstable cardiovascular function and coma do poorly because of the hypoxic-ischemic insult. Predictors are not accurate for the 15% to 20% of drowning victims whose condition on arrival is between these two extremes. However, patients who had a low Glasgow Coma Scale score upon arrival to the ED (average of 3.2 for nonsurvi vors vs. 11.6 for survivors), who required CPR, who were intubated, or for whom presser support was initiated all had a lower survival than those who did not have or require any of these. End organs can also be affected by hypoxemia and metabolic acidosis. Aspiration of substances such as contaminated foreign material, particulate matter, bacteria, vomitus, or chemical irritants can affect eventual pulmonary recovery. Electrolyte abnormalities are seldom significant and are usually transient unless there is significant hypoxia, CNS depression, renal injury from hemoglobinuria, or myoglobinuria. 8,9 Hematologic values are usually normal unless there has been massive hemolysis. Disseminated intravascular coagulation can be a complicating factor in drowning outcome but usually occurs following severe hypoxic insult. TREATMENT  PREHOSPITAL CARE Rapid resuscitation of a drowning victim (quickly restoring ventilation and oxygenation) optimizes outcome. After safe removal of the victim from the water, CPR should be initiated as quickly as possible. Trauma as a cause of drowning is uncommon, and most injured drowning patients have a history of trauma or signs of injury on examination. 10 Cervical spine injury is rare (0.5%) in drowning unless there is a history of div ing, falling from a significant height, or motorized vehicle crash. 11 Use cervical spine precautions if the history warrants it. Administer high-flow oxygen by facemask if the patient is breathing or by positive-pressure bag-valve-mask ventilation if the patient is not breathing. For patients who do not recover spontaneous respiratory effort, endotracheal intubation and positive-pressure ventilation are necessary. oxygen are used clinically in hyperbaric chambers (2.4 ATA, 2.8 ATA, and sometimes 3.0 ATA), but cerebral oxygen toxicity in this setting is rare, reported in <1 per 1000 patients. Cerebral oxygen toxicity is also affected by partial pressure of arterial carbon dioxide and cerebral blood flow and may be caused by an increase in nitric oxide production, although this is still an area of active investigation.

), but cerebral oxygen toxicity in this setting is rare, reported in <1 per 1000 patients. Cerebral oxygen toxicity is also affected by partial pressure of arterial carbon dioxide and cerebral blood flow and may be caused by an increase in nitric oxide production, although this is still an area of active investigation. Besides nitrogen narcosis and oxygen toxicity, other gas-related con ditions important in diving medicine are toxicity from carbon monoxide and the adverse effects of elevated partial pressures of carbon dioxide. Additional issues, especially with very deep dives, include heat loss from breathing helium and the high-pressure nervous syndrome, character ized by tremor and loss of fine motor function caused by the direct effects of pressure.  OTHER CONDITIONS Injuries and medical conditions occurring during and immediately after compressed air diving are often misattributed as decompression sickness or cerebral arterial gas embolism. Be aware that any medical condition can occur under the water. Acute myocardial infarction, pulmonary embolism, stroke, seizure, encephalitis, and even appendicitis have been erroneously attributed to diving. True diving accidents or cardiac sud den death can be misattributed to drowning—a common final pathway of submersion. REFERENCES The complete reference list is available online at www.TintinalliEM.com. Drowning Stephen John Cico Linda Quan INTRODUCTION AND EPIDEMIOLOGY Drowning is submersion in a liquid medium resulting in respiratory difficulty or arrest. 1 As with other causes of accidental death, drowning injury typically involves otherwise healthy, young individuals, but can involve individuals of any age or background. Worldwide, drowning accounts for >370,000 deaths annually and is the leading cause of injury death among children <15 years of age. 1 In the United States, there are >500,000 drowning events each year and 1100 deaths, which makes drowning the second leading cause of unin tentional death of individuals from birth to age 19 years old. 2,3 Although the rate of drowning deaths has decreased over the past 40 years, it remains high in low- and middle-income countries, which account for 91% of unintentional drowning deaths worldwide annually. 4 The vast majority of victims survive submersion events, with effects ranging from minimal or transient injury to profound neurologic insult. Drowning incidence peaks in three age groups: The highest is in children <5 years old, 2,3 the second peak is in those aged 15 to 24 years,2,3 and the third peak is in the elderly. 5 Toddlers drown primarily after falling into swimming pools or open water, but they also drown in bathtubs and buckets in the home. Physicians also need to evaluate for inten tional drowning (child abuse) or factitious disorder by proxy (formerly Munchausen’s by proxy). In teenagers and adults, suicide, homicide, and domestic violence can be causes of drowning. In this age group, drowning is also more likely if alcohol or drugs are involved. 6 The elderly also have an increased risk of bathtub drowning, often related to comorbid medical conditions or medications. Even in coastal areas, most drown ings take place in warm, freshwater bodies of water, especially swim ming pools. Additional injuries or disorders that either precipitate or are associ ated with drowning events are shown in Table 215-1.

of bathtub drowning, often related to comorbid medical conditions or medications. Even in coastal areas, most drown ings take place in warm, freshwater bodies of water, especially swim ming pools. Additional injuries or disorders that either precipitate or are associ ated with drowning events are shown in Table 215-1. CHAPTER TABLE 215-1 Disorders and Injuries Associated With Drowning Disorders Associated With Drowning •  Alcohol  or other intoxicants •  Syncope  (e.g., due to hyperventilation prior to underwater diving) •  Seizures •   Cardiac conditions (e.g., dysrhythmias including prolonged QT syndromes, Brugada’s syndrome, ischemic heart disease) •   Dementia •   Intentional (suicide, homicide, child abuse or neglect in young children) Injuries Associated With Drowning •   Spinal cord injuries due to diving into shallow water, significant falls from heights, or boating/personal watercraft mishaps •   Hypothermia •   Aspiration •   Respiratory failure, insufficiency, or distress Tintinalli_Sec16_p1333-1418.indd 1374 8/2/19 8:23 PM

t in young children) Injuries Associated With Drowning •   Spinal cord injuries due to diving into shallow water, significant falls from heights, or boating/personal watercraft mishaps •   Hypothermia •   Aspiration •   Respiratory failure, insufficiency, or distress Tintinalli_Sec16_p1333-1418.indd 1374 8/2/19 8:23 PM CHAPTER 215:  Drowning      1375 All patients with amnesia for the drowning event, loss of or depressed consciousness, or an observed period of apnea, as well as those who require a period of artificial ventilation, should be trans ported to an ED for evaluation, even if they are asymptomatic at the scene. The patient should be warmed and monitored, and IV access should be established (Figure 215-1).  PRIMARY ED TREATMENT Upon the patient’s arrival at the ED, assess and secure the airway, provide oxygen, determine core temperature, and assist ventilation as necessary. If the patient is hypothermic, administer warmed isotonic IV fluids and apply warming adjuncts (e.g., blankets, overhead warmers, warming devices). Address any associated injuries. Because cervical injury is rare without a history of diving or associated trauma, rou tine cervical immobilization and CT of the brain are not necessary. Patients who present to the ED with a Glasgow Coma Scale score of >13 and an oxygen saturation of ≥95% are at low risk for complications (Figure 215-1) and should be observed for 4 to 6 hours. If the pulmonary examination does not reveal rales, rhonchi, wheezing, or retractions and arterial oxygen saturation on room air remains ≥95%, the patient can be safely discharged home. Laboratory studies and radiographs are unnecessary and are not predictive of discharge. 9,12 The patient should be told to return if fever, mental status changes, or pulmonary symptoms occur. If, after 4 to 6 hours, the patient develops an oxygen requirement, the findings on pulmonary examination are abnormal (rales, rhonchi, wheeze, retractions, etc.), or the patient’s condition deteriorates, reassessment and admission or transfer to a monitored bed are needed. 9,12 Patients who present to the ED with a Glasgow Coma Scale score of <13 should be maintained on supplemental oxygen and ventilatory support as needed. If high-flow oxygen (fraction of inspired oxygen of 40% to 60%) cannot maintain an adequate partial pressure of arterial oxygen (>60 mm Hg in adults, >80 mm Hg in children), then intubate the patient and provide positive-pressure ventilation. Chest radiogra phy and laboratory studies should be done to evaluate for pulmonary aspiration and other complications (Figure 215-1). Although aspiration is common, prophylactic antibiotics have not been shown to improve outcome and may be associated with resistant infections. 13 Continuous cardiac monitoring, pulse oximetry, temperature monitoring, and fre quent reassessments should be performed for all patients. Hypothermia is a concern in patients who have been submerged in cold water (see Chapter 209, “Hypothermia”). If the patient is normothermic upon arrival in the ED and in car diopulmonary arrest or asystole, serious thought should be given to discontinuing resuscitation efforts because recovery without pro found neurologic complications is rare. 14,15  SECONDARY TREATMENT Hospital management of drowning victims is largely supportive.

atient is normothermic upon arrival in the ED and in car diopulmonary arrest or asystole, serious thought should be given to discontinuing resuscitation efforts because recovery without pro found neurologic complications is rare. 14,15  SECONDARY TREATMENT Hospital management of drowning victims is largely supportive. 16 All drowning victims who require ED resuscitation should be admitted to an intensive care unit for continuous cardiopulmonary and frequent If Sao2 <95%, or patient has abnormal physical examination (rales, rhonchi, wheezing, retractions, etc.), approach as if GCS <13 If oxygen saturations and pulmonary examination are normal, patient may be safely discharged home Clear cervical spine Oxygen saturation: Supplemental oxygen as necessary to keep Sao 2 ≥95% Endotracheal intubation and positive-pressure ventilation as needed (CPAP, PEEP) Ancillary tests: Consider CXR, CBC, electrolytes, glucose, troponin I, PT/PTT, U/A, CK, urine myoglobin, urine drug screen Monitor: Acid-base status, temperature, volume status (urine output, CVP , etc.) GCS <13 or Sao 2 <95% Observe 4–6 hours Clear cervical spine Monitor oxygen saturations Ancillary tests (usually not indicated) GCS ≥13 and Sao 2 ≥95% Submersion Event Algorithm Prehospital Care: Rapid, cautious rescue Cervical spine precautions (if injury suspected or unknown) CPR as indicated Transport (all patients) Oxygen (all patients) Emergency Department Care: Airway/breathing/circulation (address any problems) Determine GCS Treat any associated injury or condition (e.g., hypovolemia, hypothermia, seizure, myocardial infarction, etc.) Patient needs to be admitted or transported to a facility for inpatient/ICU monitoring FIGURE 215-1. Drowning event algorithm. CBC = complete blood count; CK = creatine kinase; CPAP = continuous positive airway pressure; CVP = central venous pressure; CXR = chest radiograph; GCS = Glasgow Coma Scale score; ICU = intensive care unit; PEEP = positive end-expiratory pressure; PT = prothrombin time; PTT = partial thromboplastin time; Sao2 = oxygen saturation (via pulse oximetry); U/A = urinalysis. Tintinalli_Sec16_p1333-1418.indd 1375 8/2/19 8:23 PM